Radio receiver and radio receiver front-end

ABSTRACT

A radio receiver front-end includes first and second RF receiver sections and an RF combining module. The first RF receiver section is coupled to receive an inbound RF signal and provide to a first representation of the inbound RF signal, wherein the inbound RF signal includes a desired signal component and an undesired signal component. The second RF receiver section is coupled to receive the inbound RF signal and to provide a second representation of the inbound RF signal. The RF combining module is coupled to combine the first and second representations of the inbound RF signal to produce a desired RF signal, wherein the desired RF signal includes the desired signal component and an attenuated representation of the undesired signal component.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 11/513,685, filed Aug. 30, 2006, which applicationis incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

This invention relates generally to wireless communications systems andmore particularly to radio receivers used within such wirelesscommunication systems.

2. Description of Related Art

Communication systems are known to support wireless and wire linedcommunications between wireless and/or wire lined communication devices.Such communication systems range from national and/or internationalcellular telephone systems to the Internet to point-to-point in-homewireless networks. Each type of communication system is constructed, andhence operates, in accordance with one or more communication standards.For instance, wireless communication systems may operate in accordancewith one or more standards including, but not limited to, IEEE 802.11,Bluetooth, advanced mobile phone services (AMPS), digital AMPS, globalsystem for mobile communications (GSM), code division multiple access(CDMA), local multi-point distribution systems (LMDS),multi-channel-multi-point distribution systems (MMDS), radio frequencyidentification (RFID), and/or variations thereof.

Depending on the type of wireless communication system, a wirelesscommunication device, such as a cellular telephone, two-way radio,personal digital assistant (PDA), personal computer (PC), laptopcomputer, home entertainment equipment, RFID reader, RFID tag, et ceteracommunicates directly or indirectly with other wireless communicationdevices. For direct communications (also known as point-to-pointcommunications), the participating wireless communication devices tunetheir receivers and transmitters to the same channel or channels (e.g.,one of the plurality of radio frequency (RF) carriers of the wirelesscommunication system or a particular RF frequency for some systems) andcommunicate over that channel(s). For indirect wireless communications,each wireless communication device communicates directly with anassociated base station (e.g., for cellular services) and/or anassociated access point (e.g., for an in-home or in-building wirelessnetwork) via an assigned channel. To complete a communication connectionbetween the wireless communication devices, the associated base stationsand/or associated access points communicate with each other directly,via a system controller, via the public switch telephone network, viathe Internet, and/or via some other wide area network.

For each wireless communication device to participate in wirelesscommunications, it includes a built-in radio transceiver (i.e., receiverand transmitter) or is coupled to an associated radio transceiver (e.g.,a station for in-home and/or in-building wireless communicationnetworks, RF modem, etc.). As is known, the transmitter includes a datamodulation stage, one or more intermediate frequency stages, and a poweramplifier. The data modulation stage converts raw data into basebandsignals in accordance with a particular wireless communication standard.The one or more intermediate frequency stages mix the baseband signalswith one or more local oscillations to produce RF signals. The poweramplifier amplifies the RF signals prior to transmission via an antenna.

As is also known, the receiver is coupled to the antenna and includes alow noise amplifier, one or more intermediate frequency stages, afiltering stage, and a data recovery stage. The low noise amplifier(LNA) receives inbound RF signals via the antenna and amplifies then.The one or more intermediate frequency stages mix the amplified RFsignals with one or more local oscillations to convert the amplified RFsignal into baseband signals or intermediate frequency (IF) signals. Thefiltering stage filters the baseband signals or the IF signals toattenuate unwanted out of band signals to produce filtered signals. Thedata recovery stage recovers raw data from the filtered signals inaccordance with the particular wireless communication standard.

For a receiver to reliably recover data from received inbound RF signalsit must be able to isolate desired signal components of the inbound RFsignals from interferers (e.g., interference from adjacent channel(s),interference from other devices and/or systems using frequencies nearthe frequency band of interest, and/or transmission blocking signalsthat occur in RFID systems). For example, in a cellular system, it isfairly common to have significant nearby interferers of the frequencyband of interest (e.g., one or more desired channel(s) of 5-60 MHzcentered at a frequency of about 900 MHz, 1800 MHz, 1900 MHz, and/or2100 MHz) that adversely affect the ability of a receiver to accuratelyrecover data.

One solution to reduce the adverse affects caused by interferers is touse an off-chip band pass filter (BPF) prior to the LNA to attenuate theinterferers and pass the desired channel(s). However, with nearbyinterferers (e.g., within 100 MHz), the BPF needs a steep roll off tosufficiently attenuate the interferers making it an expensive part. Inaddition, an off-chip BPF typically reduces the magnitude of the desiredchannel(s) by about 3 dB.

Another solution is to use a less expensive BPF with less roll off.While this reduces the cost and the attenuation of the desiredchannel(s), it does not sufficiently attenuate large nearby interferers.

Therefore, a need exists for a radio receiver and radio receiverfront-end that sufficiently attenuated interferers without the use ofcostly BPFs and with negligible attenuation of the desired channel(s).

SUMMARY OF THE INVENTION

The present invention is directed to apparatus and methods of operationthat are further described in the following Brief Description of theDrawings, the Detailed Description of the Invention, and the claims.Other features and advantages of the present invention will becomeapparent from the following detailed description of the invention madewith reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of a wireless communication systemin accordance with the present invention;

FIG. 2 is a schematic block diagram of a radio frequency identificationsystem in accordance with the present invention;

FIG. 3 is a schematic block diagram of a wireless communication devicein accordance with the present invention;

FIG. 4 is a schematic block diagram of an embodiment of a radio receiverfront-end in accordance with the present invention;

FIG. 5 is a schematic block diagram of another embodiment of a radioreceiver front-end in accordance with the present invention;

FIG. 6 is a schematic block diagram of another embodiment of a radioreceiver front-end in accordance with the present invention; and

FIG. 7 is a schematic block diagram of another embodiment of a radioreceiver front-end in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram illustrating a communication system10 that includes a plurality of base stations and/or access points 12,16, a plurality of wireless communication devices 18-32 and a networkhardware component 34. Note that the network hardware 34, which may be arouter, switch, bridge, modem, system controller, et cetera provides awide area network connection 42 for the communication system 10. Furthernote that the wireless communication devices 18-32 may be laptop hostcomputers 18 and 26, personal digital assistant hosts 20 and 30,personal computer hosts 24 and 32 and/or cellular telephone hosts 22 and28 that include a wireless transceiver. The details of the wirelesstransceiver will be described in greater detail with reference to FIGS.3-7.

Wireless communication devices 22, 23, and 24 are located within anindependent basic service set (IBSS) area and communicate directly(i.e., point to point). In this configuration, these devices 22, 23, and24 may only communicate with each other. To communicate with otherwireless communication devices within the system 10 or to communicateoutside of the system 10, the devices 22, 23, and/or 24 need toaffiliate with one of the base stations or access points 12 or 16.

The base stations or access points 12, 16 are located within basicservice set (BSS) areas 11 and 13, respectively, and are operablycoupled to the network hardware 34 via local area network connections36, 38. Such a connection provides the base station or access point 1216 with connectivity to other devices within the system 10 and providesconnectivity to other networks via the WAN connection 42. To communicatewith the wireless communication devices within its BSS 11 or 13, each ofthe base stations or access points 12-16 has an associated antenna orantenna array. For instance, base station or access point 12 wirelesslycommunicates with wireless communication devices 18 and 20 while basestation or access point 16 wirelessly communicates with wirelesscommunication devices 26-32. Typically, the wireless communicationdevices register with a particular base station or access point 12, 16to receive services from the communication system 10.

Typically, base stations are used for cellular telephone systems andlike-type systems, while access points are used for in-home orin-building wireless networks (e.g., IEEE 802.11 and versions thereof,Bluetooth, RFID, and/or any other type of radio frequency based networkprotocol). Regardless of the particular type of communication system,each wireless communication device includes a built-in radio and/or iscoupled to a radio. Note that one or more of the wireless communicationdevices may include an RFID reader and/or an RFID tag.

FIG. 2 is a schematic block diagram of an RFID (radio frequencyidentification) system that includes a computer/server 112, a pluralityof RFID readers 114-118 and a plurality of RFID tags 120-130. The RFIDtags 120-130 may each be associated with a particular object for avariety of purposes including, but not limited to, tracking inventory,tracking status, location determination, assembly progress, et cetera.

Each RFID reader 114-118 wirelessly communicates with one or more RFIDtags 120-130 within its coverage area. For example, RFID reader 114 mayhave RFID tags 120 and 122 within its coverage area, while RFID reader116 has RFID tags 124 and 126, and RFID reader 118 has RFID tags 128 and130 within its coverage area. The RF communication scheme between theRFID readers 114-118 and RFID tags 120-130 may be a backscatteringtechnique whereby the RFID readers 114-118 provide energy to the RFIDtags via an RF signal. The RFID tags derive power from the RF signal andrespond on the same RF carrier frequency with the requested data.

In this manner, the RFID readers 114-118 collect data as may berequested from the computer/server 112 from each of the RFID tags120-130 within its coverage area. The collected data is then conveyed tocomputer/server 112 via the wired or wireless connection 132 and/or viathe peer-to-peer communication 134. In addition, and/or in thealternative, the computer/server 112 may provide data to one or more ofthe RFID tags 120-130 via the associated RFID reader 114-118. Suchdownloaded information is application dependent and may vary greatly.Upon receiving the downloaded data, the RFID tag would store the data ina non-volatile memory.

As indicated above, the RFID readers 114-118 may optionally communicateon a peer-to-peer basis such that each RFID reader does not need aseparate wired or wireless connection 132 to the computer/server 112.For example, RFID reader 114 and RFID reader 116 may communicate on apeer-to-peer basis utilizing a back scatter technique, a wireless LANtechnique, and/or any other wireless communication technique. In thisinstance, RFID reader 116 may not include a wired or wireless connection132 to computer/server 112. Communications between RFID reader 116 andcomputer/server 112 are conveyed through RFID reader 114 and the wiredor wireless connection 132, which may be any one of a plurality of wiredstandards (e.g., Ethernet, fire wire, et cetera) and/or wirelesscommunication standards (e.g., IEEE 802.11x, Bluetooth, et cetera).

As one of ordinary skill in the art will appreciate, the RFID system ofFIG. 2 may be expanded to include a multitude of RFID readers 114-118distributed throughout a desired location (for example, a building,office site, et cetera) where the RFID tags may be associated withequipment, inventory, personnel, et cetera. Note that thecomputer/server 112 may be coupled to another server and/or networkconnection to provide wide area network coverage.

FIG. 3 is a schematic block diagram of a wireless transceiver, which maybe incorporated in an access point or base station 12 and 16 of FIG. 1,in one or more of the wireless communication devices 18-32 of FIG. 1, inone or more of the RFID readers 114-118, and/or in one or more of RFIDtags 120-130. The wireless transceiver includes a transmitter and areceiver. The receiver includes a radio receiver front-end 140, a downconversion module 142, and a receiver processing module 144. Thetransmitter includes a transmitter processing module 146, an upconversion module 148, and a radio transmitter front-end 150.

As shown, the receiver and transmitter are each coupled to an antenna,however, the receiver and transmitter may share a single antenna via atransmit/receive switch and/or transformer balun. In another embodiment,the receiver and transmitter may share a diversity antenna structure. Inanother embodiment, the receiver and transmitter may each use its owndiversity antenna structure. In another embodiment, the receiver andtransmitter may share a multiple input multiple output (MIMO) antennastructure. Accordingly, the antenna structure of the wirelesstransceiver will depend on the particular standard(s) to which thewireless transceiver is compliant.

In operation, the transmitter receives outbound data 162 from a hostdevice or other source via the transmitter processing module 146. Thetransmitter processing module 146 processes the outbound data 162 inaccordance with a particular wireless communication standard (e.g., IEEE802.11, Bluetooth, RFID, GSM, CDMA, et cetera) to produce baseband orlow intermediate frequency (IF) transmit (TX) signals 164. The basebandor low IF TX signals 164 may be digital baseband signals (e.g., have azero IF) or digital low IF signals, where the low IF typically will bein a frequency range of one hundred kilohertz to a few megahertz. Notethat the processing performed by the transmitter processing module 146includes, but is not limited to, scrambling, encoding, puncturing,mapping, modulation, and/or digital baseband to IF conversion. Furthernote that the transmitter processing module 146 may be implemented usinga shared processing device, individual processing devices, or aplurality of processing devices and may further include memory. Such aprocessing device may be a microprocessor, micro-controller, digitalsignal processor, microcomputer, central processing unit, fieldprogrammable gate array, programmable logic device, state machine, logiccircuitry, analog circuitry, digital circuitry, and/or any device thatmanipulates signals (analog and/or digital) based on operationalinstructions. The memory may be a single memory device or a plurality ofmemory devices. Such a memory device may be a read-only memory, randomaccess memory, volatile memory, non-volatile memory, static memory,dynamic memory, flash memory, and/or any device that stores digitalinformation. Note that when the processing module 146 implements one ormore of its functions via a state machine, analog circuitry, digitalcircuitry, and/or logic circuitry, the memory storing the correspondingoperational instructions is embedded with the circuitry comprising thestate machine, analog circuitry, digital circuitry, and/or logiccircuitry.

The up conversion module 148 includes a digital-to-analog conversion(DAC) module, a filtering and/or gain module, and a mixing section. TheDAC module converts the baseband or low IF TX signals 164 from thedigital domain to the analog domain. The filtering and/or gain modulefilters and/or adjusts the gain of the analog signals prior to providingit to the mixing section. The mixing section converts the analogbaseband or low IF signals into up converted signals 166 based on atransmitter local oscillation 168.

The radio transmitter front end 150 includes a power amplifier 84 andmay also include a transmit filter module. The power amplifier amplifiesthe up converted signals 166 to produce outbound RF signals 170, whichmay be filtered by the transmitter filter module, if included. Theantenna structure transmits the outbound RF signals 170 to a targeteddevice such as a base station, an access point and/or another wirelesscommunication device.

The receiver receives inbound RF signals 152 via the antenna structure,where a base station, an access point, or another wireless communicationdevice transmitted the inbound RF signals 152. The antenna structureprovides the inbound RF signals 152 to the receiver front-end 140, whichwill be described in greater detail with reference to FIGS. 4-7. Ingeneral, without the use of bandpass filters, the receiver front-end 140blocks one or more undesired signals components 174 (e.g., one or moreinterferers) of the inbound RF signal 152 and passing a desired signalcomponent 172 (e.g., one or more desired channels of a plurality ofchannels) of the inbound RF signal 152 as a desired RF signal 154.

The down conversion module 70 includes a mixing section, an analog todigital conversion (ADC) module, and may also include a filtering and/orgain module. The mixing section converts the desired RF signal 154 intoan analog baseband or low IF signal based on a receiver localoscillation 158. The ADC module converts the analog baseband or low IFsignal into a digital baseband or low IF signal. The filtering and/orgain module high pass and/or low pass filters the digital baseband orlow IF signal to produce a baseband or low IF signal 156. Note that theordering of the ADC module and filtering and/or gain module may beswitched, such that the filtering and/or gain module is an analogmodule.

The receiver processing module 144 processes the baseband or low IFsignal 156 in accordance with a particular wireless communicationstandard (e.g., IEEE 802.11, Bluetooth, RFID, GSM, CDMA, et cetera) toproduce inbound data 160. The processing performed by the receiverprocessing module 144 includes, but is not limited to, digitalintermediate frequency to baseband conversion, demodulation, demapping,depuncturing, decoding, and/or descrambling. Note that the receiverprocessing modules 144 may be implemented using a shared processingdevice, individual processing devices, or a plurality of processingdevices and may further include memory. Such a processing device may bea microprocessor, micro-controller, digital signal processor,microcomputer, central processing unit, field programmable gate array,programmable logic device, state machine, logic circuitry, analogcircuitry, digital circuitry, and/or any device that manipulates signals(analog and/or digital) based on operational instructions. The memorymay be a single memory device or a plurality of memory devices. Such amemory device may be a read-only memory, random access memory, volatilememory, non-volatile memory, static memory, dynamic memory, flashmemory, and/or any device that stores digital information. Note thatwhen the receiver processing module 144 implements one or more of itsfunctions via a state machine, analog circuitry, digital circuitry,and/or logic circuitry, the memory storing the corresponding operationalinstructions is embedded with the circuitry comprising the statemachine, analog circuitry, digital circuitry, and/or logic circuitry.

FIG. 4 is a schematic block diagram of an embodiment of a radio receiverfront-end 140 that includes a first radio frequency (RF) receiversection 180, a second RF receiver section 182, and an RF combiningmodule 184. The first RF receiver section 180 is coupled to receive theinbound RF signal 152 and provide to a first representation 186 of theinbound RF signal. Note that the inbound RF signal 152 includes adesired signal component 172 and an undesired signal component 174.

The second RF receiver section 182 is coupled to receive the inbound RFsignal 152 and to provide a second representation 188 of the inbound RFsignal. The RF combining module 184 is coupled to combine the first andsecond representations 186 and 188 of the inbound RF signal to producethe desired RF signal 154. Note that the desired RF signal 154 includesthe desired signal component 172 and an attenuated representation (e.g.,10 dB or more) of the undesired signal component 174.

FIG. 5 is a schematic block diagram of another embodiment of a radioreceiver front-end 140 that includes a first RF receiver section 180, asecond RF receiver section 182, and an RF combining module 184. In thisembodiment, the first RF receiver section 180 includes a low noiseamplifier (LNA) 190; the second RF receiver section 182 includes a LNA192 and a notch filter module 194; and the RF combining module 194includes a subtraction module.

The LNA 190 of the first RF receiver section 180 amplifies the inboundRF signal 152 to produce the first representation 186 of the inbound RFsignal. As shown, the first representation 186 of the inbound RF signalincludes the desired signal component 172 (e.g., one or more desiredchannels) and the undesired signal component 174 (e.g., interferers),but at a different magnitude than the inbound RF signal 152. Forexample, the inbound RF signal 152 may be generated in accordance with acellular system, as such, it includes a desired signal component 172 ora frequency band of interest (e.g., one or more desired channel(s) of5-60 MHz centered at a frequency of about 900 MHz, 1800 MHz, 1900 MHz,and/or 2100 MHz) and may further include a significant nearbyinterferer(s) (e.g., interference from adjacent channel(s), interferencefrom other devices and/or systems using frequencies near the frequencyband of interest, and/or transmission blocking signals that occur inRFID systems). Note that the interferers may be at frequencies within afew hundred Mega Hertz from of the frequency of the desired signalcomponent 172. Further note that the bandwidth of the received inboundRF signal 152 is at least partially dependent upon the bandwidth of theLNAs 190 and 192.

LNA 192 of the second RF receiver section 182 amplifies the inbound RFsignal 152 to produce a second amplified RF signal 198. The level ofamplification used by LNA 192 is substantially equal to the level ofamplification used by LNA 190 such that the second amplified RF signal198 is substantially equal to the first representation 186 of theinbound RF signal.

The notch filter module 194, which may include one or more notch filtershaving a total roll off of 40 dB or more, notch filters the secondamplified RF signal 198 to produce the second representation 188 of theinbound RF signal. The properties of the notch filter module 194 aresuch that the desired signal component 172 is substantially attenuatedwhile the remaining portion of the inbound RF signal 152, including theundesired signal component 174, is passed substantially unattenuated asshown. Note that the notch filter module 194 may be adjustable, wherethe notch filter adjustment is based on a channel selection signal 196.As such, the notch filter module 194 may be tuned to accommodatedifferent channels of a plurality of channels.

In another embodiment, the notch filter module 194 may include a mixerthat down-converts the second amplified RF signal 198 to a basebandsignal or an intermediate frequency (IF) signal. The notch filter module194 further includes a notch filter, low pass filter, and/or high passfilter coupled to filter the baseband signal or IF signal such that thebaseband or IF representation of the desired signal component 172 isattenuated while the baseband or IF representation of the undesiredsignal component 174 is passed substantially unattenuated. The notchfilter module 194 further includes a second mixer that mixes thebaseband or IF representation of the undesired signal component 172 withan RF or IF oscillation to produce the second representation 188 of theinbound RF signal.

The subtraction module 195 of the RF combining module 184 subtracts thesecond representation 188 of the inbound RF signal from the firstrepresentation 186 of the inbound RF signal to produce the desired RFsignal 154. As such, the desired RF signal 154 includes the desiredsignal component 172 and minimal other portions of the inbound RFsignal, including the undesired signal component 174. Thus, theinterferers are substantially attenuated without the use of bandpassfilters and without the up to 3 dB loss of the desired signal componentassociated with the use of bandpass filters.

FIG. 6 is a schematic block diagram of another embodiment of a radioreceiver front-end 140 that includes a first RF receiver section 180, asecond RF receiver section 182, and an RF combining module 184. In thisembodiment, the first RF receiver section 180 includes atransconductance low noise amplifier (LNA) 206; the second RF receiversection 182 includes a transconductance LNA 208 and a current basednotch filter module 204; and the RF combining module 194 includes a pairof current to voltage conversion modules 200 and 202 and a subtractionmodule 205.

The transconductance LNA 206 of the first RF receiver section 180amplifies the inbound RF signal 152 to produce the first representation186 of the inbound RF signal. In this embodiment, the firstrepresentation 186 of the inbound RF signal is a current-based (I)signal while the inbound RF signal 152 is a voltage-based (V) signal. Assuch, the first representation 186 of the inbound RF signal includes thedesired signal component 172 (e.g., one or more desired channels) andthe undesired signal component 174 (e.g., interferers).

Transconductance LNA 208 of the second RF receiver section 182 amplifiesthe inbound RF signal 152 to produce a second amplified RF signal 210,where the second amplified RF signal 210 is a current-based (I) signal.The level of amplification used by LNA 208 is substantially equal to thelevel of amplification used by LNA 206 such that the second amplified RFsignal 210 is substantially equal to the first representation 186 of theinbound RF signal.

The current-based (I) notch filter module 204, which may include one ormore notch filters having a total roll off of 40 dB or more, notchfilters the second amplified RF signal 210 to produce the secondrepresentation 188 of the inbound RF signal. The properties of the notchfilter module 204 are such that the desired signal component 172 issubstantially attenuated while the remaining portion of the inbound RFsignal 152, including the undesired signal component 174, is passedsubstantially unattenuated. Note that the notch filter module 204 may beadjustable, where the notch filter adjustment is based on a channelselection signal 196. As such, the notch filter module 204 may be tunedto accommodate different channels of a plurality of channels.

The current (I) to voltage (V) module 200, which may be implemented viaa transistor, a cascode transistor pair, or any circuit that converts acurrent-based signal into a voltage-based signal, converts the firstrepresentation 186 of the inbound RF signal into a voltage-based signal.The I to V module 200, which may be implemented via a transistor, acascode transistor pair, or any circuit that converts a current-basedsignal into a voltage-based signal, converts the second representation188 of the inbound RF signal into a voltage-based signal. Thesubtraction module 205 of the RF combining module 184 subtracts thesecond representation 188 of the inbound RF signal from the firstrepresentation 186 of the inbound RF signal to produce the desired RFsignal 154. As such, the desired RF signal 154 includes the desiredsignal component 172 and minimal other portions of the inbound RFsignal, including the undesired signal component 174. Thus, theinterferers are substantially attenuated without the use of bandpassfilters and without the up to 3 dB loss of the desired signal componentassociated with the use of bandpass filters.

FIG. 7 is a schematic block diagram of another embodiment of a radioreceiver front-end 140 that functions to: receive an inbound radiofrequency (RF) signal 152, wherein the inbound RF signal 152 includes adesired signal component 224 and a blocker signal 222; separate theblocker signal 222 from the desired signal component 224 to produce aseparate blocker signal 222; and produce a desired RF signal 154 fromthe inbound RF signal 152 and the separate blocker signal 222. In thisembodiment, the blocker signal 222 may be at or near the same frequencyas the inbound RF signal 152, which is typically the case for RFIDsystems.

In an embodiment, the radio receiver front-end utilizes a separationmodule 220 to separate the blocker signal from the desired signalcomponent. The separation module 220 amplifies the inbound RF signal toproduce an amplified RF signal. The separation module 220 then notchfilters the amplified RF signal to attenuate the desired signalcomponent of the amplified RF signal and to pass, substantiallyunattenuated, the blocker signal of the amplified RF signal to producethe separate blocker signal. In another embodiment, the notch filteringincludes: receiving a channel selection signal, wherein the desiredsignal component of the amplified RF signal corresponds to at least onedesired channel of a plurality of channels and wherein the at least onedesired channel is identified by the channel selection signal; andadjusting the notch filtering based on the channel selection signal.

In an embodiment, the radio receiver front-end produces the desired RFsignal from the inbound RF signal and the separate blocker signal by:amplifying the inbound RF signal to produce an amplified RF signal; andsubtracting the separate blocker signal from the amplified RF signal toproduce the desired RF signal.

As may be used herein, the terms “substantially” and “approximately”provides an industry-accepted tolerance for its corresponding termand/or relativity between items. Such an industry-accepted toleranceranges from less than one percent to fifty percent and corresponds to,but is not limited to, component values, integrated circuit processvariations, temperature variations, rise and fall times, and/or thermalnoise. Such relativity between items ranges from a difference of a fewpercent to magnitude differences. As may also be used herein, theterm(s) “coupled to” and/or “coupling” and/or includes direct couplingbetween items and/or indirect coupling between items via an interveningitem (e.g., an item includes, but is not limited to, a component, anelement, a circuit, and/or a module) where, for indirect coupling, theintervening item does not modify the information of a signal but mayadjust its current level, voltage level, and/or power level. As mayfurther be used herein, inferred coupling (i.e., where one element iscoupled to another element by inference) includes direct and indirectcoupling between two items in the same manner as “coupled to”. As mayeven further be used herein, the term “operable to” indicates that anitem includes one or more of power connections, input(s), output(s),etc., to perform one or more its corresponding functions and may furtherinclude inferred coupling to one or more other items. As may stillfurther be used herein, the term “associated with”, includes directand/or indirect coupling of separate items and/or one item beingembedded within another item. As may be used herein, the term “comparesfavorably”, indicates that a comparison between two or more items,signals, etc., provides a desired relationship. For example, when thedesired relationship is that signal 1 has a greater magnitude thansignal 2, a favorable comparison may be achieved when the magnitude ofsignal 1 is greater than that of signal 2 or when the magnitude ofsignal 2 is less than that of signal 1.

While the transistors discussed above may be field effect transistors(FETs), as one of ordinary skill in the art will appreciate, thetransistors may be implemented using any type of transistor structureincluding, but not limited to, bipolar, metal oxide semiconductor fieldeffect transistors (MOSFET), N-well transistors, P-well transistors,enhancement mode, depletion mode, and zero voltage threshold (VT)transistors.

The present invention has also been described above with the aid ofmethod steps illustrating the performance of specified functions andrelationships thereof. The boundaries and sequence of these functionalbuilding blocks and method steps have been arbitrarily defined hereinfor convenience of description. Alternate boundaries and sequences canbe defined so long as the specified functions and relationships areappropriately performed. Any such alternate boundaries or sequences arethus within the scope and spirit of the claimed invention.

The present invention has been described above with the aid offunctional building blocks illustrating the performance of certainsignificant functions. The boundaries of these functional buildingblocks have been arbitrarily defined for convenience of description.Alternate boundaries could be defined as long as the certain significantfunctions are appropriately performed. Similarly, flow diagram blocksmay also have been arbitrarily defined herein to illustrate certainsignificant functionality. To the extent used, the flow diagram blockboundaries and sequence could have been defined otherwise and stillperform the certain significant functionality. Such alternatedefinitions of both functional building blocks and flow diagram blocksand sequences are thus within the scope and spirit of the claimedinvention. One of average skill in the art will also recognize that thefunctional building blocks, and other illustrative blocks, modules andcomponents herein, can be implemented as illustrated or by discretecomponents, application specific integrated circuits, processorsexecuting appropriate software and the like or any combination thereof.

1. An apparatus comprising: a first transconductance amplifier of afirst radio receiver section to amplify an inbound radio signal andproduce a first amplified current signal that includes a desired signalcomponent and an undesired signal component; a second transconductanceamplifier of a second radio receiver section to amplify the inboundradio signal and produce a second amplified current signal that includesthe desired signal component and the undesired signal component; a notchfilter component coupled to receive the second amplified current signalto filter and attenuate frequencies about the desired signal componentof the second amplified current signal to produce a filtered secondamplified current signal; and a combining module coupled to receive thefirst amplified current signal and the filtered second amplified currentsignal, convert the first amplified current signal and the filteredsecond amplified current signal respectively to a first voltage signaland a filtered second voltage signal and to combine the first voltagesignal and the filtered second voltage signal to subtract the filteredsecond voltage signal from the first voltage signal to recover thedesired signal component from the first voltage signal.
 2. The apparatusof claim 1, wherein the first transconductance amplifier forms a lownoise amplifier at a front-end of the first radio receiver section andthe second transconductance amplifier forms a low noise amplifier at afront-end of the second radio receiver section.
 3. The apparatus ofclaim 2, wherein the notch filter is a current based filter to notchfrequencies about the desired signal component.
 4. The apparatus ofclaim 3, wherein the notch filter is an adjustable notch filter.
 5. Theapparatus of claim 4, wherein the desired signal component correspondsto a desired channel of a plurality of channels present in the inboundradio signal.
 6. A radio comprising: a first transconductance amplifierof a first receiver section to amplify an inbound radio frequency (RF)signal and produce a first amplified current signal that includes adesired signal component and an undesired signal component; a secondtransconductance amplifier of a second receiver section to amplify theinbound RF signal and produce a second amplified current signal thatincludes the desired signal component and the undesired signalcomponent; a notch filter component coupled to receive the secondamplified current signal to filter and attenuate frequencies about thedesired signal component of the second amplified current signal toproduce a notch-filtered second amplified current signal; a firstcurrent to voltage conversion module coupled to convert the firstamplified current signal to a first voltage signal; a second current tovoltage conversion module coupled to convert the notch-filtered secondamplified current signal to a notch-filtered second voltage signal; asubtraction module coupled to the first and second current to voltageconversion modules to subtract the notch-filtered second voltage signalfrom the first voltage signal to recover the desired signal componentfrom the first voltage signal.
 7. The radio of claim 6, wherein thefirst transconductance amplifier forms a low noise amplifier at afront-end of the first radio receiver section and the secondtransconductance amplifier forms a low noise amplifier at a front-end ofthe second radio receiver section.
 8. The radio of claim 7, wherein thenotch filter is a current based filter to notch frequencies about thedesired signal component.
 9. The radio of claim 8, wherein the notchfilter is an adjustable notch filter.
 10. The radio of claim 9, whereinthe desired signal component corresponds to a desired channel of aplurality of channels present in the inbound radio signal.
 11. A methodcomprising: amplifying an inbound radio signal to produce a firstamplified current signal that includes a desired signal component and anundesired signal component in a first transconductance amplifier of afirst radio receiver section; amplifying the inbound radio signal toproduce a second amplified current signal that includes the desiredsignal component and the undesired signal component in a secondtransconductance amplifier of a second radio receiver section;notch-filtering the second amplified current signal to filter andattenuate frequencies about the desired signal component of the secondamplified current signal to produce a filtered second amplified currentsignal; converting the first amplified current signal to a first voltagesignal; converting the notch-filtered second amplified current signal toa notch-filtered second voltage signal; combining the first voltagesignal and the notch-filtered second voltage signal to subtract thenotch-filtered second voltage signal from the first voltage signal torecover the desired signal component from the first voltage signal. 12.The method of claim 11, wherein amplifying the inbound radio signal atthe first radio receiver section is performed in a low noise firsttransconductance amplifier and amplifying the inbound radio signal atthe second radio receiver section is performed in a low noise secondtransconductance amplifier.
 13. The method of claim 12, wherein thenotch-filtering is performed using a current based filter to notchfrequencies about the desired signal component.
 14. The method of claim13, wherein the notch-filtering uses an adjustable notch filter.
 15. Themethod of claim 14, wherein recovering the desired signal componentrecovers a desired channel of a plurality of channels present in theinbound radio signal.